1. Field of the Invention
The invention relates to a belt force measuring device having a measuring spring whose deflection is a measure of the belt force, and having a transmitter which is associated with the measuring spring, and having a sensor element which is likewise associated with the measuring spring, with the deflection of the measuring spring effecting a change in the position of the sensor element relative to the transmitter, said change being detected by the sensor element as a measure of the belt force, and with the belt force measuring device also having a first connection element, which connects the measuring spring to at least one of a belt lock or a first belt section, and a second connection element which connects the measuring spring to at least one of a vehicle body, a component on the vehicle body, or a second belt section.
2. Description of the Prior Art
To provide improved occupant protection in a vehicle, it is necessary to measure the force a person that is strapped in transmits to the belt. This force is called the belt force. The measured values of the belt force are processed and used in the event of an accident to calculate the optimum activation of belt pretensioners and airbags.
U.S. Pat. No. 6,230,088 discloses a belt lock housing which is connected to a mounting fixed to the body of a vehicle, via a belt force measuring device. The belt force measuring device comprises a first part which is coupled to the belt lock and which has arranged on it a transmitter which is in the form of a magnet. A second part is provided which is coupled to the mounting. A sensor element which is in the form of a GMR sensor is formed on the second part. The first and second parts are coupled to one another via two springs which rest freely in each case. The belt force creates deformation of the measuring spring, with the result that the distance between the transmitter and the sensor element changes, and this is evaluated as a measurement signal for determining the belt force.
DE 102 43 344 B4 discloses a belt force measuring device having a measuring spring whose expansion is used as a measure of the belt force. A belt lock housing, which is connected to a mounting via the belt force measuring device, is fixed to the body of a vehicle. The belt force measuring device comprises a first separate connection element, which is coupled to the belt lock, and a second separate connection element which is coupled to the mounting. The connection elements are coupled to one another via the measuring spring. The belt force measuring device also has a transmitter, which is arranged on the measuring spring in a fixed position in relation to a first bearing of the measuring spring, and a sensor element which is arranged on the measuring spring in a fixed position in relation to a second bearing of the measuring spring. The measuring spring is arranged and formed such that it expands between the first and second bearing as a function of the belt force.